The present invention relates to fluid jet devices of the type which deposit drops of coating fluid from a plurality of jet drop streams on a fluid receiving medium and, more particularly, to such a device in which a simplified structure is provided for electrically charging, deflecting and catching drops in the jet drop streams to prevent their deposit upon the medium.
Numerous jet drop recorders, printers, and fluid coating devices have been utilized in the past to control the application of drops of fluid to a fluid receiving medium, such as a sheet of paper or a paper or fabric web. U.S. Pat. No. 3,787,881, issued Jan. 22, 1974, to Duffield, discloses a bar code printer in which a pair of charge electrodes is provided for gang charging groups of jet drop streams positioned in a single row. A separate deflection electrode and a conductive drop catcher are positioned on opposite sides of the row of jet drop streams for deflecting and catching the groups of drops which are charged in ganged fashion.
U.S. Pat. No. 4,122,458, issued Oct. 24, 1978, to Paranjpe, discloses an ink jet printer in which drops in each of the jet drop streams positioned in a row are charged by a single charge electrode. Deflection electrodes, associated with individual ones of the jet drop streams, thereafter control the trajectories of drops in each of the streams in order to provide selective printing of the drops in each stream at one of a plurality of print positions on a print receiving medium. The charge electrode and the deflection electrodes form part of a multi-layer structure, with sheets of insulating material sandwiched therebetween to provide electrical insulation.
U.S. Pat. No. 3,656,171, issued Apr. 11, 1972, to Robertson, discloses a jet drop recording device in which an associated one of a plurality of charge electrodes is positioned adjacent each of the jet drop streams in a row of such streams. Charged drops move past a conductive surface and induce on the surface a corresponding electrical charge which attracts the charged drops toward a drop catcher. Uncharged drops produce no such induced charge on the conductive surface and, therefore, travel past the conductive surface and the catcher, and strike the print receiving medium.
U.S. Pat. No. 3,656,174, issued Apr. 11, 1972, to Robertson, discloses another form of printer operating on the same deflection principle described above with respect to the Robertson U.S. Pat. No. 3,656,171. A circular array of jet drop streams pass downward through a single charge electrode which is configured as a hollow cylinder. If a charge potential is applied to the electrode, all of the drops in the jet drop streams are charged. These charged drops thereafter induce corresponding surface charges of opposite polarity on the interior surface of the cylinder. The charged drops are therefore deflected outward toward the cylinder surface and are caught by an apertured catcher plate positioned beneath the charge electrode.
U.S. Pat. No. 4,123,760, issued Oct. 31, 1978, to Hou, discloses an ink jet printer in which an assymmetrical charging and deflection field is selectively applied to jet drops emanating from a fluid filament with the result that the jets may be deflected to strike a catcher face. The charging and deflection field is produced by a pair of electrodes positioned to either side of the fluid filament and extending generally perpendicular to the face of the catcher.
U.S. Pat. Nos. 1,817,098, issued Aug. 4, 1931, to Ranger et al, and 1,941,001, issued Dec. 26, 1933, to Hansel, disclose printers using electrostatic jet deflection which do not include separate charge electrodes. Deflection electrodes in the disclosed printers receive deflection potentials to deflect drops selectively to a separate drop catcher structure.